How to Build a Chimney Cricket (Saddle) and Flash It
A small peaked roof behind the chimney that splits the water and snow and steers them around. Needed on wide chimneys.
- Professional
- 4 to 8 hours
- Updated
The short answer
A chimney cricket, or saddle, is a small peaked roof framed on the upslope side of a chimney to divert water around it. The BC Building Code requires one where the upslope side of the chimney is more than 750 mm (about 30 inches) wide. Frame two triangular planes from a ridge, sheath them, cover with ice and water shield and metal, and lap the metal over the step flashing and under the roof above.
Water and snow running down a roof meet the upslope face of a chimney head on. On a narrow chimney they split and run around the sides. On a wide chimney they cannot, and they pile up behind the masonry, sit in a dam, and find every gap in the flashing. A cricket, also called a saddle, fixes that by making a small peaked roof behind the chimney, so the flow is split at the ridge and carried around both sides.
The BC Building Code requires a chimney saddle, which is the code's word for a cricket, where the upslope side of a chimney on a sloping roof is more than 750 mm (about 30 inches) wide. The only way around it in the code is taller flashing: metal running up the chimney at least one sixth of its width and not less than 150 mm, and up the roof at least 1.5 times the shingle exposure, with counter flashing over it. Confirm with your local building department, which may have its own requirements. Narrower chimneys use a back pan. Everything here ties into the other chimney flashing parts.
Tools
- Framing square
- Circular saw
- Tape measure
- Speed square
- Roofing hammer or nailer
- Tin snips (straight cut and offset)
- Sheet metal brake
- Chalk line
Materials
- 2 by 4 lumber for the ridge and cripples
- 1/2 inch plywood for the planes
- Ice and water shield
- Galvanized, prefinished steel or copper sheet for the cricket covering
- Framing nails and roofing nails
- Polyurethane or hybrid polymer sealant
Safety first
- Work tied off. A cricket is built at the ridge side of the chimney on a sloped roof. WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall could cause serious injury.
- You will be cutting lumber on a slope. Cut on the ground where you can, and keep the roof clear of offcuts that roll.
- Sheet metal edges are sharp. Wear cut resistant gloves and use a sheet metal brake rather than bending by hand.
Step by Step
Step 1: Check whether a cricket is needed
Measure the face of the chimney that faces upslope. If it is more than 750 mm (about 30 inches), the BC Building Code calls for a cricket. Some roofers build one on narrower chimneys too on very steep roofs or in heavy snow country, because snow and debris dam behind any chimney. Check with your local building department for any added requirement.
Step 2: Lay out the cricket on the deck
A cricket is two triangular planes that meet at a short ridge against the chimney and slope away to the sides. The planes meet the roof in valleys that run from the upslope end of the ridge down to the chimney corners. Snap a line from the centre of the chimney face up the roof for the ridge.
A common layout rule is that the cricket's ridge height at the chimney equals half the chimney width times the roof's rise per foot divided by 12. For a 36 inch wide chimney on a 6/12 roof, half the width is 18 inches, times 6/12 is 9 inches of ridge height. Lay out the ridge length so the planes have a pitch similar to the roof.
Step 3: Frame the ridge and cripples
Cut a 2 by 4 to the ridge length and support it at the chimney end with a short post or fastened to a blocking piece, with its top at the layout height. Run the ridge up the roof and let it die into the roof plane at its upper end. Frame short cripples along the two valley lines from the ridge to the chimney corners, each cut to the right height and angle.
Nail into rafters wherever possible, and never frame into the chimney masonry. Leave the recommended clearance between the framing and the masonry, following local code.
Step 4: Sheath the two planes
Use 1/2 inch plywood or the same thickness as the roof deck. Cut each plane as a triangle, with the top edge against the ridge and the bottom edges following the valleys. Keep the plywood tight to the framing, and use enough fasteners to keep it from lifting. See how to replace roof sheathing for decking practice.
Keep the plywood back from the chimney face by the required clearance, then seal the gap with membrane and metal.
Step 5: Cover the cricket with ice and water shield
Start at the lower valley ends and work up, so each upper piece laps over the one below. Press the membrane into the corners and lap it onto the chimney face and the roof deck. Keep nails out of the valleys and the ridge. See how to install ice and water shield.
Step 6: Cover the cricket with metal and tie it into the flashing
The metal cricket covering has a ridge fold and two planes, with its upper end tucked up under the roof's underlayment and shingles, at least 6 to 8 inches, and its bottom end turned up the chimney face. Its sides lap over the top step flashing pieces. Fasten the metal only along the upper edges. On a large cricket, shingles can cover the planes instead, with a metal ridge and valleys.
The counter flashing then covers the turned-up metal on the chimney face. See how to install chimney counter flashing.
Step 7: Seal the joints and test
Fold metal corners rather than cutting and gluing, and use sealant only as a backup. Run a hose at the top of the cricket for 10 to 15 minutes and watch. Water should split at the ridge and flow out over the step flashing on both sides, not pool behind the chimney. Check the attic for any moisture at the chimney.
Snow and Debris Behind Chimneys
A cricket matters even more in snow country. At Hope and up the Fraser Canyon, wet heavy snow slides down the roof and piles behind the chimney, where a flat back pan holds it against the flashing while it melts and refreezes. A steeper cricket sheds snow to both sides instead. Needles and leaves also collect behind a chimney without a cricket, and keep the flashing wet.
Cricket Materials
A metal-covered cricket is the most durable and is the usual choice on a chimney. A shingled cricket can look cleaner but requires the valleys to be properly flashed and adds more joints. For a large cricket, consider a membrane and metal for the valleys and shingles elsewhere. Always check the shingle manufacturer's instructions for minimum pitch on the cricket planes.
Common Mistakes
- No cricket on a wide chimney. Water and snow pond behind the masonry and find every gap.
- Too flat. A cricket with too little pitch holds water and debris, and defeats its purpose.
- Framing into the masonry. The chimney and roof move independently, and framing needs clearance.
- Metal not lapped under the roof above. Water from above runs under the cricket covering.
- Cricket metal lapped under the step flashing. The cricket must lap over the top step flashing pieces.
- Nails in the valleys. The valleys of a cricket carry all the split water and must be free of nails.
- Covering rot. A cricket built over damaged decking hides the problem.
When to Call a Professional
A cricket involves framing, sheathing, membrane and metal work at the ridge side of a chimney, where the roof is often steep and tall. If the chimney is wide, the roof is steep or the deck near the chimney is soft, hire a roofer. The cricket, step flashing and counter flashing should be built as one system.
If you are not sure the chimney needs one, a roofer can tell you from the width, the slope and the snow load in your area.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Repair service or the towns we cover.
How to Build a Chimney Cricket (Saddle): Questions
What is a chimney cricket?
A chimney cricket, also called a saddle, is a small peaked roof built on the upslope side of a chimney. Two sloped planes meet at a short ridge against the chimney and run down to its corners. It splits the water, snow and debris coming down the roof and carries them around both sides instead of letting them pool behind the chimney.
How wide does a chimney need to be for a cricket?
The BC Building Code requires a cricket, which it calls a chimney saddle, where the upslope side of a chimney is more than 750 mm (about 30 inches) wide, unless the flashing is run much higher up the chimney and the roof. Narrower chimneys use a back pan. Many roofers also build one on narrower chimneys on steep roofs or in snow country, and your local building department can confirm any added requirement.
How high should a chimney cricket be?
A common layout rule sets the ridge height at the chimney equal to half the chimney width times the roof's rise per foot divided by 12. A 36 inch wide chimney on a 6/12 roof gives a ridge height of about 9 inches. The planes should have enough pitch to shed water and snow, similar to the roof itself.
Can a cricket be covered with shingles?
Yes, on larger crickets with enough pitch, but the valleys and the ridge still need metal or membrane, and the shingle manufacturer's minimum pitch applies. A metal covering is the most durable and has fewer joints. Whichever you use, the cricket must lap over the top step flashing pieces and tuck under the roofing above.
Related Guides
All Chimneys guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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